Sigma 8-16mm Review (Long with many images)

Started Jun 8, 2010 | Discussions
Severian The Lame
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Sigma 8-16mm Review (Long with many images)
Jun 8, 2010

As a UWA virgin I had been looking intently for several months into the possibility of acquiring either the Canon 10-22 or the Tokina 11-16 and had pretty much settled on the Tokina. The problem was that it just never seemed to be in stock at any of the reputable online dealers. Then Sigma threw a monkey wrench into my calculations by announcing the 8-16, and all of a sudden 10 and 11mm seemed just so passé and ridiculously narrow! I’m joking, but only a little. Despite the inherent risks of being an early adopter of a third party lens, once this lens became available I just couldn’t resist. I picked it up almost four weeks ago and in that time I’ve easily snapped over 2200 shots, both testing and playing around and with more serious intent as well. I must say that I’m both impressed and at the same time a little disappointed, too. (Which has been pretty much my experience, one way or another, with all four of the Sigma lenses I own.)

I called this a review in the thread title, but this is basically a few observations. I have uploaded to my gallery several samples of the shots I’ve taken. I had also intended to upload some shots specifically for this post and as examples of various things I’ve found out about my copy of this lens but I ran afoul of the gallery space limitations. I was able to get a few up but have since taken them down and moved everything I was going to put there to photobucket. [ http://s838.photobucket.com/albums/zz305/daPriceIs/Product_Shots/Photo_Gear/Sigma_8-16mm/ ] There you can find essentially an extended version of this “review” by reading the photo titles and captions (and looking at the images, of course).

This review is going to be quite long and contain many photos so I'm going to break it up into a series of a few posts. This first post will concentrate on the build of the lens.

  • Build : The focus and zoom rings have a nice smooth feel (not an "L" silkiness, but still very nice) yet are firm without being stiff. The lens is a little more hefty than the Sigma 50mm f/1.4 and is all in all a substantial piece of glass.

    • If you know anything about this lens then you will have heard about it's bulbous and potentially vulnerable front element.

      The front elements (FEs) are minimally protected by a permanently affixed hood. I say minimally because there is always some exposure. From about 12-13mm to 16mm the FEs are recessed.

      From somewhere between 13 and 12mm down to 8m the FEs extend outward. At full extension the FEs extend beyond the protection of the smaller petals of the hood.

      But even when fully retracted at 16mm the FE extends a bit beyond the notch between the small and large petals of the hood.

    • Sigma has provided some additional protection for the lens in the form a black anodized aluminum ring that fits snugly around the hood allowing a standard 72mm lens cap to clip into place.

      Sigma calls this ring a "lens cap adapter" so I will too.

      The adapter has two pads glued inside it to grip the hood. They feel and look like suede dyed black. They seem durable enough and look to be easily replaceable when they wear out.

    • You will no doubt have noticed that the end of the adapter is threaded. That's right, it'll accept a 72mm filter. Here I have it mounted with a 77mm CPL via a step up ring.

    • There will, of course, be significant vignetting. In the category of “I do stupid things so you don’t have to,” I took some test shots with the adapter in place, both with and without a filter installed. Vignetting is insane at 8mm but perhaps acceptable at 16mm, especially if you crop a bit.

8mm + Adapter +CPL

12mm + Adapter + CPL

16mm + Adapter + CPL

I'll cover distortion, flare, and CA in my next post.

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Sloopies
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Thanks!
In reply to Severian The Lame, Jun 8, 2010

Really appreciate this post and the great information in it!
Looking forward to the rest of it
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Fabian628
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Re: Sigma 8-16mm Review (Long with many images)
In reply to Severian The Lame, Jun 8, 2010

was this adapter intended to be used while taking pictures or is it just a way to attach a lens cap?
It seems a little pointless shooting with it on
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Severian The Lame
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Sigma 8-16mm Review: Distortion, Flare, and CA
In reply to Severian The Lame, Jun 8, 2010
  • Distortion

    • There is a tiny amount of pincushion at 16mm, but not usually relevant.

    • There is the expected barrel distortion at 8mm. It’s not horrendous but it can get your attention. A lot of the time the image will be so overwhelmed with edge distortion and perspective effects that the barreling won’t be noticed.

    • o I took several test shots to demonstrate the distortion at 8mm, but none of them were interesting. The best examples came by accident while trying to shoot something else. Those examples are really striking and reveal a much more complicated distortion at 8mm than anything I was expecting.

  • Flare

    • It can exhibit some rainbow colored flare when very intense lights sources are at or very near an image corner. This flare is many stops less bright than its source and is thus not very visible if its source is not too blown out. However, let the light source (the sun, for instance) be very blown and then the flare becomes glaring.

    • But that little green golf ball on the purple tee is basically about as bad as it gets without getting into really contrived situations (I won't bore you with the night shots with flare induced by an LED flashlight.)

    • Due to the front element and the extremely wide FOV, there can be bits of flare even when the source of the flare is not in the image itself or even close to being in the image. This is especially true at 8mm.

Here that little red football by the bus is caused by the sun which is very far out of the frame.

    • Here's a counterexample. The stadium lights below on the left are the kind of night lighting that can cause multiple ghosts on my Sigma 50/1.4 or Canon 28-135 IS, but they present no problem for the 8-16.

    • Bottom line, I don’t consider the flare that it exhibits to be all that bad. But it can sneak up on you sometimes when shooting in intense sunlight even when you think the sun is well outside of the frame. It’s just one more little thing (among many) to keep in mind while composing your shots with this lens.

  • Chromatic Aberration

    • CA is omnipresent but not bad. I routinely correct every shot no matter what focal length or aperture –though admittedly my lens seems to be stuck at 8mm and f/8. Here are two 100% crops of a 7D images and are examples of basically as bad as it gets!

This is excellent for a zoom lens. My EF 70-200 f/4 IS often produces a bit more CA than this. Even pixel peeping on a 7D there is little to object to.

Next post: centering and focusing.

[Unfortunately I have to sleep and go to work, etc. So it will be hours before I can make my next post.]

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Severian The Lame
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Re: Sigma 8-16mm Review (Long with many images)
In reply to Fabian628, Jun 8, 2010

It's just a mechanism to attach a lens cap. No sane person would use it the way I did. I'm just saying you could if so inclined.

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martin brech
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Re: Sigma 8-16mm Review: Distortion, Flare, and CA
In reply to Severian The Lame, Jun 8, 2010

thanks a lot for your good job. Very interesting.
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Fabian628
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Re: Sigma 8-16mm Review (Long with many images)
In reply to Severian The Lame, Jun 8, 2010
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Montana500
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Re: Sigma 8-16mm Review (Long with many images)
In reply to Severian The Lame, Jun 8, 2010

Nice review. Thx for posting.

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Severian The Lame
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Sigma 8-16mm Review: Centering and Focusing
In reply to Severian The Lame, Jun 9, 2010

Centering and Focusing

  • Two other copies of this lens featured in threads in the Canon lens forum exhibited symptoms of centering problems as did the copy reviewed by photozone. One other forum member posted a thread with photos from his gallery but there was no mention of centering and I haven’t examined them to find out. (Also some threads on this lens in the Nikon lens forum but I haven't paid much attention to them.) So that’s at least three out of four with centering issues –not a good sign. You can now make that at least four out of five; though in my case (and apparently that of LSHorwitz1) the lens’ symptoms are fairly benign and mostly cured by stopping down to f/8 plus I've discovered a work around when shooting at infinity as in the following examples.

  • In the examples below I shot at 8mm at f/4.5, f/8, and f/11. The first shot at each aperture is with the 7D’s battery grip in normal portrait position and the second with it upside down. (As a curious side note, in my tests the 7D’s “evaluative” metering overexposes 1/3 of a stop when upside down! And in case you're wondering about the obviously incorrect time stamps on the photos: the camera's clock is set to UTC.)

  • I had a hell of a time trying to get all of these handheld shots (almost) identically framed. Trying to do the same trick with the camera mounted on a tripod presents its own difficulties. But rotating the camera isn’t really necessary; all you actually need is a frame filling subject with a proper degree of rotational symmetry and fine detail. So I tried next to shoot an ISO 12233 test chart ( http://www.graphics.cornell.edu/~westin/misc/res-chart.html ). To fill the frame at 8mm I had to stick the front of the lens about 6 inches from a chart printed at 19x13 inches. And that caused me all kinds of lighting difficulties. Not to mention problems getting everything aligned, etc. etc. If you look carefully at the resultant test shots you’ll soon see that not everything is kosher. Hey, best I could do, especially given that the whole procedure was so mind-numbingly tedious that I just couldn’t face doing it again. My hat’s off to all of you that do this kind of thing for a living. (Question: how do you stay awake?! )

  • All of the aforementioned problems and limitations of the test methodology mean that my results are not even remotely definitive, though they do show to my satisfaction that a problem exists. As a lawyer might say, my results are indicative but not probative.

  • I won’t post all that tedious mess here, but the curious can view it in all its glory at http://s838.photobucket.com/albums/zz305/daPriceIs/Product_Shots/Photo_Gear/Sigma_8-16mm/Centering/

  • One thing I have found is that (on my copy at least) this problem is focus related. I have shot many landscapes where I don’t notice any issue at all but have virtually identical shots of the same subject where the problem is clear. The only difference I could discern by examining EXIF data and fiddling around with camera and lens settings has to do with the recorded subject distance, i.e., exact position of the focus ring. I would have thought at 8mm and f/8 for subjects mostly at infinity that the DOF would make precise focusing not that critical. But my copy’s defect means that’s not true. Yeah, it’s true for the center, but not for the periphery, especially the upper right corner in landscape orientation. Taking a close look at the lens internals as seen through the front element and referring to Sigma’s published diagram ( http://www.sigma-photo.co.jp/english/lens/digital/8_16_45_56.htm ) you can see how the inner focus groups of elements work and how they move back and forth and rotate.

MFD

Beyond Infinity

  • Given that the center stays sharp while one side of the image varies my guess is that the problem lies squarely with these elements and is related to their rotation and not to their travel and that in the full image circle the misfocusing is still present; it just gets rotated off of the upper right corner of the rectangular sensor. It would be really interesting to test this: all I would need is a full frame camera and a replacement for the lens that I and my Dremel tool would destroy! Do I have any sponsors? A few test shots can be found here: http://s838.photobucket.com/albums/zz305/daPriceIs/Product_Shots/Photo_Gear/Sigma_8-16mm/Focusing/

Autofocus

  • Sigma lenses often make autofocus an adventure. So how does this lens autofocus on the 7D? It’s hard to say for sure but at close focus distances of a meter or less it seems to work OK. At longer distances? In one sense it’s all over the place. I use either single point or spot focus mode on the 7D and I can get what I’m focusing on in focus with any of the 19 points. (OK, OK. I mostly use the center point and shift to others as necessary, so I haven’t methodically checked every point.) But refocusing on the same point in the same scene can get the lens hopping back and forth as shown in the focus window, sometimes quite significantly. And the indicated focus distance can differ substantially between normal AF and Live View AF (contrast) even though the results in terms of subject sharpness are the same.

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Severian The Lame
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Sigma 8-16mm Review: Conclusion
In reply to Severian The Lame, Jun 9, 2010

This lens is impressive and fun to use but challenging to master.

The build is excellent. It's sharp wide open at every focal length. Flare and ghosting are not a serious problem. Chromatic aberration is a non-issue.

On the other hand: at 8mm it exhibits significant (but typical) barrel distortion which contains components that cannot easily be completely removed with standard software tools. Also there appears to be a good deal of sample variation (based on various other posts) and several reports of copies that are at least mildly decentered.

My bottom line is that I'm happy to own this lens even though I found out early on that it has some issues. I did not return the lens because: a) I really wanted the it and knew if I returned it it would just be to get another; b) multiple reports of other copies having the same problem led me to conclude that my chances of getting a better copy weren't as good as my chances of getting a worse (especially considering that I and another had both gotten our lenses from Adorama at about the same time and his appeared to be worse than mine); c) the problem, while definite and needing of correction, was not severe. In other words it wasn't returned because I thought it more likely that servicing the lens I already had would yield a better result than RMA roulette. Moreover, I've since discovered a workaround that solves the problem for my typical uses of this lens.

My question now is, which is the best Sigma service center for this kind of thing?

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technic
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Re: Sigma 8-16mm Review: Centering and Focusing
In reply to Severian The Lame, Jun 9, 2010

Severian The Lame wrote:

Centering and Focusing

  • Two other copies of this lens featured in threads in the Canon lens forum exhibited symptoms of centering problems as did the copy reviewed by photozone.

same story with the Canon 15-85IS. Many copies around with some centering problems and one bad border/corner. I guess other WA zooms with an 'ambitious' design will show similar variation when examined carefully.

  • In the examples below I shot at 8mm at f/4.5, f/8, and f/11.

those are not full size examples? f/4.5 still looks pretty good to me, but difficult to judge at this size.

  • One thing I have found is that (on my copy at least) this problem is focus related. I have shot many landscapes where I don’t notice any issue at all but have virtually identical shots of the same subject where the problem is clear. The only difference I could discern by examining EXIF data and fiddling around with camera and lens settings has to do with the recorded subject distance, i.e., exact position of the focus ring. I would have thought at 8mm and f/8 for subjects mostly at infinity that the DOF would make precise focusing not that critical. But my copy’s defect means that’s not true. Yeah, it’s true for the center, but not for the periphery, especially the upper right corner in landscape orientation. Taking a close look at the lens internals as seen through the front element and referring to Sigma’s published diagram ( http://www.sigma-photo.co.jp/english/lens/digital/8_16_45_56.htm ) you can see how the inner focus groups of elements work and how they move back and forth and rotate.

interesting, I have the same problem with the Canon 15-85 at WA end of the range, and others have confirmed. Corners/ borders at infinity tend to be soft. The problem varies between shots while using the same fl, e.g. 15mm. I first thought this variation was caused by the IS unit, but later found it also occurs with IS off. The 15-85 tends to frontfocus in the WA range (not at the tele end), at least on some of the Rebel bodies, which usually increases the border sharpness problem. It is strange that the problem increases with frontfocus, because this lens shows some field curvature at 15mm where close objects seem to be sharper - one would guess that frontfocusing makes infinity objects even softer.

It might be the same issue you mention, caused by lens groups/elements that move during focusing or zooming. Just like with your Sigma this is a bit strange problem, because officially the DOF should easily cover a huge range.

My Canon 18-55IS lens had a similar problem with soft corners/borders at the WA end of the range, but ONLY if the camera was pointed strongly upwards. In normal orientation corners were always sharp even wide open. This also varied between shots and I haven't been able to nail down the cause, but I'm suspecting mechanical play of lens elements during focusing.

  • Given that the center stays sharp while one side of the image varies my guess is that the problem lies squarely with these elements and is related to their rotation and not to their travel and that in the full image circle the misfocusing is still present; it just gets rotated off of the upper right corner of the rectangular sensor.

I don't think it works like that. I'm guessing that the lens elements are not moved exactly along the optical axis, or maybe their own axis varies a little bit while they move. This is most likely due to mechanical tolerances in the parts of the lens barrel that guide the focusing/zooming actin.

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Severian The Lame
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Re: Sigma 8-16mm Review: Centering and Focusing
In reply to technic, Jun 9, 2010

technic wrote:

Severian The Lame wrote:

Centering and Focusing

  • In the examples below I shot at 8mm at f/4.5, f/8, and f/11.

those are not full size examples? f/4.5 still looks pretty good to me, but difficult to judge at this size.

No. I uploaded to my gallery half-sized samples; i.e., 1728x2592. If you click the original image link you'll see that. I thought that was big enough to show the problem without taking up too much space in the gallery. I have no clue how DPR downsized the images when I embedded them in my post. I don't know what happened with that first shot at f/4.5 because it looks worse than is typical; something odd was definitely going on there. That's one of the reasons I abandoned the 'rotate the camera' approach.

It might be the same issue you mention, caused by lens groups/elements that move during focusing or zooming. Just like with your Sigma this is a bit strange problem, because officially the DOF should easily cover a huge range.

My Canon 18-55IS lens had a similar problem with soft corners/borders at the WA end of the range, but ONLY if the camera was pointed strongly upwards. In normal orientation corners were always sharp even wide open. This also varied between shots and I haven't been able to nail down the cause, but I'm suspecting mechanical play of lens elements during focusing.

I often shoot skylines from the roof of a 30 storey building and will occasionally notice some oddities in sharpness across the frame which may be related to the downward angle I'm shooting at. It's hard to put a finger on.

  • Given that the center stays sharp while one side of the image varies my guess is that the problem lies squarely with these elements and is related to their rotation and not to their travel and that in the full image circle the misfocusing is still present; it just gets rotated off of the upper right corner of the rectangular sensor.

I don't think it works like that. I'm guessing that the lens elements are not moved exactly along the optical axis, or maybe their own axis varies a little bit while they move. This is most likely due to mechanical tolerances in the parts of the lens barrel that guide the focusing/zooming actin.

I have no clue, really. But that was my theory. You may very well be right.

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